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Solutions of hydroxypropylmethylcellulose (HPMC) and polyvinyl alcohol (PVA) are widely used as artificial tears. However, their usefulness is limited by the short duration of their effect. Dilute sodium hyaluronate (SH) solutions exhibit non-Newtonian rheology with high viscosities at low shear rates, which would be expected to enhance their ocular surface residence time. Using quantitative 7 scintigraphy, estimates of the ocular surface residence times of 0.3% HPMC, 1.4% PVA, and 0.2% SH were made in six patients with keratoconjunctivitis sicca. The sodium hyaluronate solution had a mean half-life on the ocular surface of 321 s, significantly longer than hydroxypropylmethylcellulose (44 s; p=0.012) and polyvinyl alcohol (39 s; p=0.013).